A Task-Based Approach to Parallel Restricted Hartree–Fock Calculations

Abstract

In recent years, parallelism via multithreading has become extremely important to the optimization of high-performance electronic structure theory codes. Such multithreading is generally achieved via OpenMP constructs, using a fork-join threading model to enable thread-level data parallelism within the code. An alternative approach to multithreading is task-based parallelism, which displays multiple benefits relative to fork-join thread parallelism. A novel Restricted Hartree−Fock (RHF) algorithm, utilizing task-based parallelism to achieve optimal performance, was developed and implemented into the JuliaChem electronic structure theory software package. The new RHF algorithm utilizes a unique method of shell quartet batch creation, enabling construction and distribution of fine-grained shell quartet batches in a load-balanced manner using the Julia task construct. These shell quartet batches are then distributed statically across message-passing interface (MPI) ranks and dynamically across threads within an MPI rank, requiring no explicit inter-rank or interthread synchronization to do so. Compared to the hybrid MPI/OpenMP RHF algorithm present in the GAMESS software package, the task-based algorithm demonstrates speedups of up to ∼40% for systems in the S22(3) test set of molecules, with system sizes up to ∼1000 basis functions. The JuliaChem algorithm demonstrates the viability of both the task-based parallelism model and the Julia programming language for construction of performant electronic structure theory codes targeting systems of a size of chemical interest.

ipie: A Python-Based Auxiliary-Field Quantum Monte Carlo Program with Flexibility and Efficiency on CPUs and GPUs

“…49 Thus, we next discard 50 blocks for equilibration and reblock the remaining 150 blocks to produce an estimate of the energy and its error bar. The resulting energy is −5.3825 (7), which is comparable to the energy of CCSD(T), −5.3841. Note that the above example is for demonstration purposes only.…”

“…The development of new electronic structure methods can often be accelerated by programs written in high-level, interpreted languages such as Python and Julia. Prominent recent examples are , , , , , , , , and . If programs written in such high-level languages reach similar performance compared to other production-level programs written in Fortran or C++, much more scientific development can be achieved at a faster pace.…”

The General Atomic and Molecular Electronic Structure System (GAMESS): Novel Methods on Novel Architectures

“…JuliaChem, developed by Poole, Galvez Vallejo, and Gordon, ,, showcased a native Julia implementation of the RHF method. Julia showed promise in writing quantum chemistry code in two important ways.…”